1. Field
Exemplary embodiments of the present invention relate to a method of growing gallium nitride-based semiconductor layers and a method of fabricating a light emitting device, and more particularly, to a method of growing gallium nitride-based semiconductor layers and a method of fabricating a light emitting device using metal-organic chemical vapor deposition.
2. Discussion of the Background
Generally, group-III nitrides such as gallium nitrides (GaN) have excellent thermal stability and a direct transition type energy band structure. Accordingly, gallium nitride compound semiconductors have been broadly studied for application to light emitting devices, such as light emitting diodes or laser diodes, which emit visible and ultraviolet light. In particular, blue and green light emitting diodes using indium gallium nitride (InGaN) have been used in a wide range of fields, such as large natural color flat display devices, signal lights, indoor lighting, high density light sources, high resolution output systems, optical communication, and the like.
In the manufacture of semiconductor devices, gallium nitride compound semiconductor layers are generally grown on a substrate through metal-organic chemical vapor deposition (MOCVD). An apparatus for MOCVD includes a chamber for loading a substrate, and source gas and atmosphere gas (including carrier gas) are supplied to grow an epitaxial layer on the substrate under a predetermined chamber pressure.
Commercially obtained MOCVD apparatuses may be generally configured to grow epitaxial layers at low pressures of about 200 Torr or less. Such a low pressure MOCVD apparatus can achieve relatively rapid growth of the epitaxial layer, but may create a high density of crystal defects, particularly point defects, in the epitaxial layer. As a result, the epitaxial layer may have low crystal quality.
Moreover, when the low pressure MOCVD apparatus is used to grow well layers in an active layer, growth temperature may be lowered to, for example, about 750° C. in order to increase the content of In in the well layers.
Further, when a barrier layer is grown on the well layer at the low growth temperature of the well layer, it may be difficult for the barrier layer to have good crystal quality. Thus, a method of growing a barrier layer by raising the growth temperature after growth of a well layer has been adopted. For an active layer including a plurality of well layers and a plurality of barrier layers, the temperature of the substrate within the chamber requires frequent variation, thereby increasing a processing time for growth of the active layer. Furthermore, when the substrate temperature is raised after growth of the well layer, the well layer may decompose, thereby causing deterioration in crystal quality of the well layer near an interface between the well layer and the barrier layer. To solve such a problem, a cap layer may be formed before growth of the barrier layer, but the cap layer may still fail to provide desirable interface characteristics between the well layer and the barrier layer.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any part of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.